In order to form films using a MOCVD method (a metalorganic chemical vapor deposition method), a showerhead-type MOCVD apparatus is conventionally used. In the showerhead-type MOCVD apparatus, a source gas introduced into a showerhead through an introducing line is supplied into a chamber through a shower plate to grow epitaxial films on a wafer in the chamber.
The MOCVD method is used, for example, when a stacked film having a superlattice structure such as an LED (Light Emitting Diode) or a HEMT (High Electron Mobility Transistor) is to be formed. For example, when a superlattice such as AlN/GaN layers is to be formed, films of respective layers need to be formed without source gases corresponding to the films being mixed with each other to provide steepness in a composition change at interfaces between the films of the respective layers.